1. Field of the Invention
The present invention relates to a fluid analyzer used for example, design of a housing environment and a program-recording medium.
2. Description of the Related Art
Because of recent advancement and spread of a large high-speed computer capable of performing vectorizing computation or simultaneous parallel processing, a system is widely used which generates a computing grid in a large space having a complex boundary condition and then, generates a group of equations for expressing changes and states of various substances by a physical law for controlling changes of substances in the space, and solves the equations through repetitive computation. For example, a flat-plate stress analyzer using the finite element method is an example of the above system in a wide meaning and FIDAP and NASTRAN are also examples of programs used for the system.
Physical laws, formulas, and arts which are premises of these analyses such as the techniques for grid division (mesh division) of a space to be analyzed when using, for example, the mass conservation law, momentum conservation law, energy conservation law, coordinate transformation, finite difference method, or finite element method, how to provide a decision value or boundary condition used for deciding whether to perform repetitive computation for a predetermined difference, the technique for repetition when performing repetitive computation, the technique for solving a group of equations configuring a determinant, and the technique for simultaneous parallel processing by a large high-speed computer are, so to speak, publicly-known arts published in, for example, Fluid Engineering of Volume A5 of xe2x80x9cMechanical Engineering Handbookxe2x80x9d edited by Japan Society of Mechanical Engineers and issued in 1987 and xe2x80x9cNumerical Analysis of Heat Movement and Flow by Computerxe2x80x9d written by SUHASU. V. PATANKA (transliterated) and translated by Yukio Mizutani and Shoji Kogetsu, and published byMORIKITA SHUPPAN (transliterated), in which fluid analysis results are also published in Summary Collection (China) of Academic Lectures of Congress of Architectural Institute of Japan, published in October, 1990. Therefore, their description is omitted. Moreover, because computation of pressure, momentum, mass, and calorie or computation of correction values of physical values, specifically, increase of calorie of a fluid by a value equivalent to decrease of momentum and thereby, correcting density or flow rate, and previously input of various physical property values such as density and viscosity corresponding to each temperature and pressure of a fluid necessary for the above computations are self-evident arts. Therefore, their description is omitted.
Then, one of the above techniques will be specifically described below.
1. The contents of an external force serving as a cause of a flow such as the shape of a space to be analyzed, the physical property value and flow rate of an internal fluid, and various formulas and physical laws used for analyses are inputted through CRT or a keyboard.
2. The grid division of a space to be analyzed is performed in accordance with a predetermined procedure. In this case, a grid interval (size) and arrangement position are designated by an analyzer in principle.
3. The number of times for repetitive computation is inputted by an analyzer.
4. Repetitive computation of fluid analysis is started.
5. It is decided whether physical values meet various formulas and physical laws used for analysis, for example, the difference between the computation result obtained in the last cycle and the computation result obtained in the present cycle converges to a predetermined value.
6. When the decision result converges to the predetermined value, the cycle of repetitive computation ends. However, if the result does not converge, a new cycle of repetitive computation is started.
However, when using these conventional methods, if an object and a fluid having physical property values different from each other are mixed, the length of a cell serving as the unit of the minimum size grid-divided to simplify a formula for thermal conduction is equalized between adjacent cells. Therefore, when a thin-flat object or a narrow space is present, the grid interval is decreased between at least adjacent cells of objects having physical property values different from each other in order to perform accurate analysis.
In this case, the grid interval is inevitably decreased under the above state. Therefore, when computing every space to be analyzed in three dimensions, computation frequently falls into an undesired state from viewpoints of storage resource and computation speed required by a computer.
Moreover, when setting a speed vector as a boundary condition, an outlet or inlet is set so that the speed vector coincides with a momentum vector. Therefore, whenever angles of an outlet or inlet vector are changed, a grid must be regenerated. Thus, a problem occurs that a lot of time is necessary.
Furthermore, to perform the steady computation of natural convection, a flow field becomes very unstable and computation diverges. Therefore, problems occur that even an expert of analysis must adjust the setting of a boundary condition and perform computation again.
Therefore, it is requested to realize an analyzer capable of accurately setting a physical property value in accordance with grid division information for object arrangement and boundary conditions, performing one-dimensional or two-dimensional computation in a three-dimensional space, adjusting a momentum in accordance with the momentum vector for outlet or inlet without correcting grid division, and automatically setting a boundary condition not diverged in natural-convection computation.
The present invention is made to solve the above problems of a conventional analyzer and its object is to provide a fluid analyzer capable of further decreasing the computation time.
The 1st invention of the present invention is a fluid analyzer having a grid generation section for generating the grid of an analysis space in order to analyze the fluid in the analysis space, comprising:
physical-property value setting means for setting a new physical-property value in accordance with different physical values when adjacent cells among cells each of which is a minimum unit determined by the generated grid show physical property values different from each other; and
number-of-dimension control-analysis means for (1) performing first analysis of the analysis space of a predetermined dimension by considering the adjacent cells as a larger-size new cell and using the new cell and the set physical property value and (2) replacing a partial region including the adjacent cells with a space at a dimension lower than the predetermined dimension, performing second analysis of the partial region in accordance with the original size of the adjacent cells and reflecting the result of the second analysis on the result of the first analysis.
One aspect of the present invention is a fluid analyzer comprising:
a grid generation section for generating the grid of an analysis space;
a boundary condition setting section for setting a boundary condition to the grid generated by the grid generation section;
fluid physical-value analysis section for computing the predetermined physical value of a fluid in accordance with given formula and boundary condition;
a fluid physical-value correction-analysis section for approximately correcting a result by the fluid physical-value analysis section in accordance with the fluid state of a pressure distribution and/or a speed distribution computed by the fluid physical-value analysis section and the physical property value of each physical value of a previously-given fluid or a predetermined physical law; and
a repetitive-computation and control section for repeating computations from the fluid physical-value analysis section up to the fluid physical-value correction-analysis section in accordance with a predetermined procedure; wherein
a physical-property-value setting section is included which sets a new physical property value in accordance with at least the position of an object and grid information including the divided state of the grid.
Another aspect of the present invention is a fluid analyzer, wherein the predetermined physical value is the pressure, speed, density, or temperature of the fluid, the predetermined physical law is the mass conservation law, momentum conservation law, or energy conservation law, and a number-of-dimension control-analysis section is included which performs analysis as a one-dimensional or two-dimensional space in some or all regions in the three-dimensional space of the grid generated by the grid generation section.
Still another aspect of the present invention is the fluid analyzer, wherein a momentum correction section is included which automatically corrects the momentum of a speed vector set to an outlet or inlet provided for the analysis space in accordance with the divided state of a grid and the information for an outlet or inlet angle.
Yet another aspect of the present invention is the fluid analyzer, wherein a boundary condition control section is included which controls the boundary condition of an outlet or an inlet in accordance with the boundary condition set by the boundary condition setting section.
Still yet another aspect of the present invention is the fluid analyzer, wherein the predetermined physical value is tile pressure, speed, density, or temperature of the fluid and the predetermined physical law is the mass conservation law, momentum conservation law, or energy conservation law.
A further aspect of the present invention is a program recording medium storing a program for making a computer execute some or all of means or sections of the fluid analyzer.